In a data processor, a high speed memory has been built in to enhance a performance. For example, a high speed memory having a built-in data processor is provided in the address space of a CPU (central processing unit) in the same manner as an external memory and is thus used. Moreover, the built-in memory is utilized as a cache memory to constitute a cache system, thereby increasing the speed of a memory access. The former example has been disclosed in JP-A-5-307485 publication and the latter case has been disclosed in JP-A-6-103064 publication.